The disunity of “Mysidacea” (Crustacea)

Abstract

New studies on malacostracan relationships have drawn attention to issues concerning monophyly of the order Mysidacea, manifested in recent crustacean classiWcations that treat the taxon as two separate orders, Lophogastrida and Mysida. We present molecular phylogenies of these orders based on complete sequences of nuclear small-subunit ribosomal DNA (18S rRNA), and morphological evidence is used to revise the classiWcation of the order Mysida to better reXect evolutionary history.A secondary structure model for 18S rRNA was constructed and used to assign putative stem and loop regions to two groups of partitions for phylogenetic analyses. Phylogenies were estimated by maximum-likelihood, Bayesian inference, and maximum-parsimony. The analyses gave strong support for three independently derived lineages, represented by three monophyletic groups, Lophogastrida, Stygiomysida, and Mysida. The family Petalophthalmidae is considered as sister group to the family Mysidae, and Boreomysinae and Rhopalophthalminae are the most early derived of the Mysidae. The tribes contained in the current classiWcation of the subfamily Mysinae are not well-supported by either molecular data or morphology.

The first Paleozoic stenopodidean from the Huntley Mountain Formation (Devonian–Carboniferous), north-central Pennsylvania

“…Many of the resultant topologies were interesting with respect to the position of pygocephalomorpha within Peracarida. For example, in a number of the topologies obtained, Tealliocaris resolved within Pygocephalomorpha in a clade composed of Mysida + Lophogastrida + Pygocephalomorpha, as the sister group to the rest of Peracarida, supporting previous hypotheses that pygocephalomorphs comprise part of a monophyletic 'Mysidacea,' although 'Mysidacea' is generally considered to be polyphyletic (SCHRAM 1984;MELAND & WILLASSEN 2007). In a number of the trees, Tealliocaris resolved within Pygocephalomorpha with Pygocephalomorpha as the sister group to the higher peracarids, and Lophogastrida and Mysida as the sister group to Peracarida as a whole.…”

Phylogenetic relationships of the family Sphaeromatidae Latreille, 1825 (Crustacea: Peracarida: Isopoda) within Sphaeromatidea based on 18S-rDNA molecular data

“…Primary sequence and secondary structure have been worked out for several crustaceans including the isopod Armadillidium vulgare (Choe et al 1999), the mysid Boremysis megalops (Meland 2007), and used in higher-level arthropod phylogeny by Koenemann et al (2009). In addition to consideration of secondary structure further sampling is required to address the composition of Sphaeromatidea as proposed by Brandt & Poore (2003).…”

Mysid (Crustacea: Mysidacea) Distribution in the Bolgoda Estuarine System and Lunawa Lagoon, Sri Lanka

“…They belong to the Superorder Peracarida and the Order Mysidacea, although a recent classification (Melland & Willassen, 2007) places them in the Order Mysida. This reflected better evolutionary history.…”